Sea Level Rise
There are two mechanisms that cause sea levels to rise. One is the thermal expansion of ocean waters (steric), contributing to roughly 50% of the sea level rise observed in the past century; as water warms, its particles expand, taking more volume and thus occupying more space (COAPS, 2021). Oceans have absorbed more than 90% of the extra heat from the planet in the past 50 years (NOAA, 2021). The second cause is the melting of glaciers and continental ice sheets, adding more volume to ocean waters. In addition, this ice cover melting reduces the albedo effect (reflection of sunlight back to the atmosphere), which further contributes to warming the oceans and the melting of glaciers and ice sheets (COAPS, 2021).
Sea level rise has been historically estimated through a network of tide gauges that accurately measure the local height of water surfaces. However, measuring global sea level rise rates is a complex task due to global variations in land surface elevation and tide gauges locations, thus to help accurately measure sea level rise, altimeter satellites are used to calculate the height of the sea surface from space. Since Florida does not have a significant geologic process, the sea level rise rates at most monitoring stations along the coast are closely aligned with global rates. However, with this tool, it can be observed that sea level rise is not uniform around the world. Satellite estimates indicate that areas with warmer waters have higher rates of sea level rise. Nonetheless, it is important to note that regardless of this non-uniform rise rate, studies have shown that sea level rise rates are accelerating around the world in recent years, transitioning away from previous decades’ steady pace. In addition, nuisance or sunny day flooding events (high tide flooding) are observed and estimated to continue to become 3 to 4 times more common due to rising sea levels (COAPS, 2021).
Sea level rise can have detrimental impacts on coastal communities and considerable effects in inland areas, and the East Central Florida region is no exception to these risks. Some of the effects include amplified storm surges and flooding, destructive erosion, wetland flooding, saltwater intrusion (including aquifer and agricultural soil saltwater contamination), flora and fauna habitat loss, infrastructure damage, and human life risk, which also bring along significant economic loss. Thus, it is important to plan for future land use accordingly in anticipation of potential sea level rise risks and mitigate current impacts.
In the East Central Florida region, there are two coastal counties- Brevard and Volusia- at evident risk of sea level rise impacts. Thus, the East Central Florida Regional Resilience Action Plan’s Sea Level Rise Projection Sub-committee identified a regional approach to planning for sea level rise. The purpose of this approach is to provide local governments and regional agencies with a coordinated and vetted method to planning for sea level rise. Planning recommendations include the incorporation of upper and lower bound projections scenarios (refer to the graphs below for all relative sea level rise rate curves and 2100 projections and upper and lower bound scenarios), and diverse use of projections for planning- no one projection rate curve should be used for planning purposes across all projects and programs. Instead, a range of rise should be considered based upon the vulnerability, allowable risk, project service life, and the forecast project "in-service' date of a facility or development. The range should include a minimum rise of 5.15 feet by 2100 (2013 U.S. Army Corps of Engineers (USACE) High) with an upper range of 8.48 feet by 2100 (2017 NOAA High). Short-term planning should consider impacts out to 2040 (20-year planning horizon), medium-term planning should consider impacts out to 2070 (50-year planning horizon), and long-term planning should extend out to 2100 (80-year planning horizon).
ECF Regional Resiliency Action Plan Bounds for Planning Sea Level Rise
The upper bound is the sea level rise estimate associated with NOAA 2017 high rate curve. This scenario is recommended for assessment and adaptation, mitigation, and minimization planning of places with little risk tolerance and long functional life span, new/proposed (re)development, or significant intensification on previously minimally developed land that may be on future fringes of vulnerable areas. On the other hand, the lower bound scenario considers the USACE 2013 high rate curve or minimum planning of 5.15 feet of sea level rise by 2100. This minimal planning level is recommended for places that are less vulnerable, have a greater risk tolerance to flooding, are of little impact in terms of the health, safety, and welfare of a community.